Conventional underwater propulsion systems are formed in the manner of torpedoes and the principal flow resulting from rotation of the propeller is ejected along the axis of symmetry of the device.
The diver must therefore be offset with respect to this axis, and the beam in the direction of the displacement becomes increased.
There thus results a rocking force, operator fatigue, and energy loss. On the other hand, the maneuverability is strongly affected by the relative position of the diver with respect to the propulsion device. High speeds cannot be attained by this type of device.
FIG. 1 shows such a conventional propulsion device, in which the diver must be shifted along the axis OZ so as to be displaced above the turbulence generated by the propeller.
One prior art solution consists of placing two turbo-motors on both sides of the propulsion device, as shown in DE-A-35 23 758, but this solution is complex and costly.